1. Field of the Invention
The present invention relates to a wireless communication system. More particularly, the present invention relates to an apparatus and a method for enhancing performance using Precoding Matrix Index (PMI) cycling or PMI repetition in an open loop multi-cell Multiple Input Multiple Output (MIMO) system.
2. Description of the Related Art
Research has led to the development of next generation mobile communication systems such as a 4th Generation (4G) communication system or International Mobile Telecommunication (IMT)-Advanced.
The next generation communication systems are based on an Institute of Electrical and Electronics Engineers (IEEE) 802.16m standard or a 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) Advanced standard. These standards adopt an Orthogonal Frequency Division Multiplexing (OFDM)/Orthogonal Frequency Division Multiple Access (OFDMA) scheme in order to support a broadband network in a physical channel.
However, in such a system, a mobile station traveling in or around the edge of a base station can suffer from interference. This interference is referred to as inter-cell interference.
A multi-cell Multiple Input Multiple Output (MIMO) system is an efficient method for mitigating the inter-cell interference. Using this method, a cell edge and cell average throughputs can be enhanced and base station coverage area can be expanded.
However, a closed loop multi-cell MIMO system is subject to PMI aging because of feedback delay and backhaul delay of the mobile station.